FIG. 1 illustrates a conventional database network. The network comprises a plurality of clients 102, a network server 104, a Web Sphere™ server 106, and a bases a database 108 containing objects. The WebSphere server 106 is an applications server, developed by International Business Machines. Corp.™, which functions as an extension to the network server 104. The WebSphere server 106 allows users to write object-oriented application programs and to design or install custom objects. These objects are stored as table structures in the database 108. The WebSphere server 106 is typically used with relational database systems, such as DB2™ or Oracler™.
As is well known in the art, the objects in the database 108 have class definitions. The class definitions contain information concerning static properties in the objects 108. Static properties are the attributes defined in the class definition. Each of the static properties are mapped to a table column in the database 108, and this mapping data is stored as metadata. The metadata takes the similar form of a Structured Query Language (SQL) view and the query translation processes are based on relational view rewrite. Some objects also have dynamic property capabilities. Dynamic properties on the contrary are not defined in the class definition. They are typically used for customizing an application without changing the class definition. They can be accessed using getPropertyBy and can be set using setPropertyBy methods that are defined in the class definition. By storing these data as dynamic properties, the user need not change the object's class definition each time a dynamic property is added or deleted. As with static properties, the dynamic properties may each be mapped to a table column in the database 108. Alternatively, one or more of them may be unmapped, and instead be stored in an overflow column.
Oftentimes, a user wishes to execute queries on the objects in the database 108. The WebSphere server 106 contains a query service 110 for this purpose. For static properties, the query refers to the attributes of the class definitions for the objects. Using metadata, the query system translates the query into a query against the database schema, and this is referred to as “pushdown”. If a query contains a method, instances of objects must be created and methods must be run on these instances, and this is referred to as running “in object space”. Because dynamic properties are accessed using the methods, evaluating the queries with dynamic properties is done in object space. Running queries in object space is usually slower than pushdown, and thus is inefficient.
Accordingly, there exists a need for a method for efficient object query on dynamic properties. The present invention addresses such a need.